Adobe Camera RAW -> Photoshop. If I use just ACR for minor editing in PP, I'll just save a JPG since the xmp file will retain the edits made. If I do more work in PS I'll save a JPG and a PSD file (retains layers). If it's HDR (photomatix) I'll import the CR2 files into photomatix, save a TIFF, and then work with the TIFF in PS.

I use Adobe RAW to make adjustments in RAW, then open as a smart object in Photoshop. Make a new Smart Object layer (not a duplicate layer) and then open that layer in RAW to make adjustments to other areas of the image. Do this as many times as needed to tweak all the areas. Use layer masks and the paintbrush tool to reveal or cover up portions that I want/don't want in each layer.

I tend to save all my layers in Photoshop (psd) in case I ever need/want to go back and tweak the image.

I'll save a final copy as a JPEG (often two copies, one for printing and one for the web). I end up having the original RAW file, one PSD file and one or more JPEG files. (A small one for the web, a large one for printing) Probably not the most space efficient, but it gives me flexibility. I know I can always go back to the original RAW file and start over, or I can pick up in the middle with the PSD file if I want to try a different look.

From doing a bit of research...it appears that you cannot work directly with RAW images in Adobe Photoshop.

Of course you can open RAW files in PS...that's what ACR (Adobe Camera Raw) is. It's embedded in PS just as Bridge is embedded. It's a very fine RAW processor using an identical processing engine to Lightroom. LR just offers more workflow options, particularly useful when working on a lot of files, but the output is identical.

When i want to work with an image I open it in DPP, make some changes there, the use the "transfer to Photoshop" command. It does not save the file in any particular format, the file just opens in photoshop as a 16 bit image. From there i will always save in Photoshop's native .psd format.

Well, one of my main reasons for the question here...is to do some HDR work.

I found that most things won't take RAW for HDR manipulations...so, would TIFF be better than jpg to work with when moving between applications, such as HDR stuff (Photomatix, etc).

I'm getting that Photoshop has the PSD...but I'm not gonna have access to that tool for awhile I don't think....so, for work outside of Photoshop, or the Adobe Suite in general...what would be the best non-RAW format to work with?

TIFF was used for print back in the day before jpegs could support CMYK color with variable levels of compression. I find no reason to use TIFF anymore (TIFF can also preserve layers, which might be useful for sending files between PS and gimp?). Not sure, I dont use gimp so i havent tested that. Either way, a PDF can do everything a TIFF can + more.

As far as saving the most efficient flattened file, if working with a file that is going to be printed massive and viewed close (best quality), I'd work in CMYK color and save a flat version of my PSD as a PDF. Otherwise, there is no real reason NOT to save something flat as a jpeg (or PNG).

The benefit of using a PDF is that it's viewable by pretty much everyone, but can preserve vectors and photoshop layers potentially if someone reopens it with PS.

TIFF was used for print back in the day before jpegs could support CMYK color with variable levels of compression. I find no reason to use TIFF anymore (TIFF can also preserve layers, which might be useful for sending files between PS and gimp?). Not sure, I dont use gimp so i havent tested that. Either way, a PDF can do everything a TIFF can + more.

As far as saving the most efficient flattened file, if working with a file that is going to be printed massive and viewed close (best quality), I'd work in CMYK color and save a flat version of my PSD as a PDF. Otherwise, there is no real reason NOT to save something flat as a jpeg (or PNG).

The benefit of using a PDF is that it's viewable by pretty much everyone, but can preserve vectors and photoshop layers potentially if someone reopens it with PS.

Maybe I am forgetting something...?

TIFF support 16Bits per channel while JPEG only supports 8bit.

Thats the only reason I would export TIFF to the client. If they want additional editing done elsewhere, They have that extra data there.